In PCB wiring, zvinowanzoitika kuti tambo yakatetepa inofanirwa kushandiswa kupfuura nenzvimbo ine nzvimbo shoma yewiring, uyezve tambo ichidzoreredzwa kuhupamhi hwepakutanga. Shanduko muhupamhi hwemutsara inokonzeresa shanduko muimedance, iyo inoguma nekuratidzira uye kukanganisa iyo chiratidzo. Saka ndirini patinogona kufuratira izvi, uye ndirini patinofanira kufunga nezve maitiro azvo?

Zvinhu zvitatu zvine hukama nemhedzisiro iyi: kukura kweiyo impedance shanduko, nguva yekumuka kwechiratidzo, uye kunonoka kwechiratidzo pamutsetse wakamanikana.

Kutanga, kukura kweiyo impedance shanduko inokurukurwa. Dhizaini yemaseketi mazhinji inoda kuti ruzha runoratidzwa ruve pasi pe5% yemhepo inofamba (inoenderana nebhajeti ruzha pachiratidzo), zvinoenderana neyakaenzana fomura:

Iyo yekufungidzira shanduko mwero wemhedheni inogona kuverengerwa se △ Z / Z1 ≤ 10%. Sezvaungave iwe uchiziva, iyo chaiyo chiratidzo cheiyo impedance pabhodhi iri +/- 10%, uye ndicho chikonzero chikonzero.

Kana iyo impedance shanduko ikaitika kamwe chete, senge panowanikwa mutsetse upamhi kubva pa8mil kuenda pa6mil uye yasara 6mil, iyo impedance shanduko inofanirwa kunge iri pasi pe10% kuitira kuti usvike pane ruzha bhajeti chinodikanwa kuti chiratidzo chinoratidza ruzha pakushanduka kamwe kamwe isingadariki 5% yeiyo voltage swing. Izvi dzimwe nguva zvinonetsa kuita. Tora nyaya yemitsetse ye microstrip pamahwendefa eFR4 semuenzaniso. Ngativerengei. Kana hupamhi hwehupamhi hwakaita 8mil, ukobvu pakati pemutsara nereferensi ndege iri 4mil uye iyo impedance ine 46.5 ohms. Kana hupamhi hwesimbi hwachinja kuita 6mil, iyo impedance inova 54.2 ohm, uye iyo impedance shanduko inosvika 20%. Iko kukura kwechiratidzo chinoratidzwa kunofanirwa kupfuura muyero. Kana iri yekukanganisa kwakadii kune iyo chiratidzo, asiwo neiyo chiratidzo yekukwira nguva uye kunonoka kwenguva kubva kumutyairi kuenda kune yekuratidzira poindi chiratidzo. Asi ingangoita dambudziko dambudziko. Neraki, iwe unogona kugadzirisa dambudziko ne impedance inoenderana netemu.

Kana iyo impedance shanduko ikaitika kaviri, semuenzaniso, mutsetse upamhi unoshanduka kubva 8mil kusvika 6mil, uyezve inoshanduka kudzokera ku8mil mushure mekuburitsa 2cm. Zvino muna 2cm kureba 6mil yakafara tambo kumakona maviri echiratidziro, imwe ndiyo impedance inova hombe, kuratidzira kwakanaka, uyezve iyo impedance inova diki, isina kunaka kuratidzwa. Kana iyo nguva iri pakati pekufungisisa ipfupi zvakakwana, iwo maratidziro maviri anogona kukanzurana kunze, zvichideredza mhedzisiro. Kufunga kuti chiratidzo chekufambisa i1V, 0.2V inoratidzwa mune yekutanga yakanaka kuratidzwa, 1.2V inopfuudzwa kumberi, uye -0.2 * 1.2 = 0.24V inoratidzwa kumashure muchiratidziro chechipiri. Kufunga kuti kureba kwetambo ye6mil ipfupi zvakanyanya uye iwo maviri maonerwo anoitika panenge panguva imwe chete, iyo yakazara inoratidzirwa voltage ingori 0.04V, yakaderera pane iyo ruzha bhajeti inodiwa ye5%. Naizvozvo, kunyangwe uye zvakadii kuratidzwa uku kunokanganisa chiratidzo kunoenderana nenguva yekunonoka pane iyo impedance shanduko uye iyo chiratidzo yekukwira nguva. Zvidzidzo uye kuyedza zvinoratidza kuti sekureba sekunge kunonoka kune impedance shanduko kuri pasi pe20% yenguva yekukwira kwechiratidzo, chiratidzo chinoratidzwa hachizokonzere dambudziko. Kana iyo chiratidzo yekukwira nguva iri 1ns, saka kunonoka pane iyo impedance shanduko iri pasi pe0.2ns inoenderana ne1.2 inches, uye kuratidzira harisi dambudziko. Mune mamwe mazwi, mune ino kesi, 6mil yakafara waya kureba isingasviki 3cm haifanire kunge iri dambudziko.

Kana iyo PCB wiring upamhi ichichinja, inofanirwa kunyatso kuongororwa maererano nemamiriro chaiwo kuti aone kana paine chinokanganisa. Pane matatu matatu ma parameter ekuti unetseke nezve: yakadii iyo impedance inoshanduka, inguva yakadii chiratidzo inomuka nguva, uye yakareba sei mutsipa-senge chikamu chemutsara upamhi chinoshanduka. Gadzira kufungidzira kwakaomarara zvichibva nenzira iri pamusoro uye siya mamwe margin sezvakakodzera. Kana zvichibvira, edza kudzikisa hurefu hwemutsipa.

Izvo zvinofanirwa kuratidzwa kuti mune chaiko PCB kugadzirisa, parameter haigone kuve yakajeka seiya ari mune dzidziso. Dzidziso inogona kupa nhungamiro kune yedu dhizaini, asi haigone kuteedzerwa kana kuomerera. Mushure mezvose, iyi sainzi inoshanda. Iko kukosha kwakatarwa kunofanirwa kuongororwa maererano nemamiriro ezvinhu chaiwo, uye wozoshandiswa kune dhizaini. Kana iwe uchinzwa usina ruzivo, chengetedza uye gadzirisa pamutengo wekugadzira.